PROCESS OF PREPARING COPPER PHTHALOCYANINE PARTICLES EXHIBITING ALPHA CRYSTALLOGRAPHIC FORM

摘要

There is provided a process of preparing copper phthalocyanine (CuPc) particles exhibiting an alpha crystallographic form, which comprises the following steps: (a) mixing crude copper phthalocyanine particles containing at least 50 wt % of particles exhibiting a beta crystallographic form with an acid in the presence of CuPc particles substituted by at least one functional group, such that at least part of the crude CuPc is dissolved in the acid; and (b) precipitating at least part of the dissolved CuPc in a medium. By adding CuPc derivatives in the acid-pasting step for the phase conversion from beta to alpha crystallographic type CuPc, the entire process time of producing blue pigments based on epsilon-CuPc, as well as the performance of the color filter pigment containing them, can be improved.